2002 年 6 巻 2 号 p. 83-97
Volcanic ash soils are distributed exclusively in regions where active and recently extinct volcanoes are located. The soils cover approximately 124 million hectares, or 0.84% of the world’s land surface. While, thus, volcanic ash soils comprise a relatively small extent, they represent a crucial land resource due to the excessively high human populations living in these regions. However, they did not receive worldwide recognition among soil scientists until the middle of the 20th century. Development of international classification systems was put forth by the 1978 Andisol proposal of G. D. Smith. The central concept of volcanic ash soils was established after the finding of nonallophanic volcanic ash soils in Japan in 1978. Nowadays, volcanic ash soils are internationally recognized as Andisols in Soil Taxonomy (United States Department of Agriculture) and Andosols in the World Reference Base for Soil Resources (FAO, International Soil Reference and Information Centre and International Society of Soil Science). Several countries including Japan and New Zealand have developed their own national classification systems for volcanic ash soils. Finally correlation of the international and domestic classification systems is described using selected volcanic ash soils.
